1. Field of the Invention
The present invention relates to a wireless communication system, and more specifically, to an apparatus and method for controlling inter-cell interference.
2. Discussion of the Related Art
Binary Power Control (BPC)
Methods for mitigating inter-cell interference in a cellular network include a method of controlling transmit power, a method of dividing a frequency used between cells, a method of dividing a sector, etc. The method of controlling transmit power reduces transmit power when a cell applies severe interference to a neighboring cell to mitigate the interference and increases the transmit power when the cell applies insignificant interference to the neighboring cell to enable high-throughput transmission to a UE of the cell.
Recent researches has determined that a method of setting one of minimum power and maximum power as transmit power or determining transmit power as an on/off state is the best control method to maximize capacity of multi-cell network (maximize a utility function as necessary). This method is called binary power control (BPC). A method of defining an on/off state of each base station as a pattern on the basis of BPC and a resource allocation method for scheduling UEs at a base station that is on in the defined pattern have been proposed.
Almost Blank Subframe (ABS)
In LTE-A, a slot of 0.5 ms includes 6 or 7 symbols and 12 subcarriers (180 KHz) and a 1 ms subframe consisting of 2 slots is a minimum resource allocation unit. 10 subframes form a frame.
In LTE-A, a base station does not transmit data to a UE during one subframe, which is called an almost blank subframe (ABS), in order to eliminate inter-cell interference in the time domain. For example, the ABS is used in such a manner that ABSs are provided during aggressor cell transmission that causes inter-cell interference such that a victim cell has high throughput at a low interference level.